Locking mechanism



May 27, 1952 R. A. FIRMAN LOCKING MECHANISM 2 SHEETS-SHEET l Filed June 50, 1948 INveivTol? May 27,- 1952 R. A. FlRMAN LOCKING MECHANISM 2 SHEETS-SHEET 2 Filed June 50, 1948 I/vve R W4. M

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to the actuator,

Patented May 27, 1952 7 LOCKING MECHANISM Reginald Arthur Firman, Weybridge, England,

assignor to Vickers-Armstrongs Limited, London, England Application June 30, 1948, Serial No. 36,239 In Great Britain October 3, 1947 2 Claims.

This invention has reference to locking mechanism of the kind in which a braced linkage is caused to collapse as the result of a lateral blow from a rotary actuator, the linkage being held in the braced position prior to collapse by a holding member constituting part of the rotary actuator. Such a mechanism forms the subject of United States patent specification Serial No. 764,800, now Patent No. 2,548,053. In this mechanism a rotary armature has two abutments adapted to act laterally on either side of a braced linkage of a toggle mechanism, the collapse of such linkage having the efiect of unlocking a releasable attachment to which the mechanism is applied. Normally the armature is unenergised and is then resiliently biassed so that one of the abutments acts as a holding member to press the linkage against a stationary abutment and so hold it in the braced position. When the armature is energised electromagnetioally it is caused to rotate in opposition to the resilient bias so that the second abutment delivers a lateral blow to the linkage and so causes it to collapse.

Whilst the said known mechanism has been proved capable of withstanding shocks of a very high order without inadvertent release of the locking mechanism it is appreciated that there is a risk of failure in this respect when the device is subjected to certain shocks of greater severity, such as those produced by explosions, or the still more severe conditions relating to shocks of a hammer-blow character, and the object of the present invention is to provide means whereby the safety of the mechanism may be increased to such an extent that it will cater for shocks of this nature.

In a locking mechanism of the kind referred to there is provided, according to the present invention, a damping or shock-absorbing member which is interposed between the holding member and the linkage. This shock-absorbing member may take the form of a pad of resilient material such as felt, india-rubber or leather or may alternatively consist of a wire or other spring. The function of this member is to absorb any shock which might be transmitted from the linkage and which might be of sufficient magnitude to cause the actuator to rotate and collapse the linkage.

It is also desirable to reduce the possibility of lateral shocks being transmitted to the linkage from the casing and for this reason it is important to eliminate any stationary abutment on the casing against which the linkage may be pressed in the braced position. Such an abutment is provided in the mechanism described in United States patent specification Serial No. 764,800/47 for the purpose of preventing the linkage passing the aligned position. When such an abutment is eliminated it is necessary to make the linkage self-aligning so that it can collapse only towards the run-away position of the linkage.

Two embodiments of the invention will now be described with reference to the accompanying drawings as applied to the mechanism described in United States patent specification Serial No. 764,800/47 to which specification reference is made for a complete description of the details of operation.

In the drawings:

Fig. 1 shows the mechanism with the linkage in the braced position and including a resilient pad as the shock-absorbing member;

Fig. 2 shows the mechanism of Fig. 1 with the linkage in the collapsed position;

Fig. 3 shows the mechanism in the same position as in Fig. l but having the shock-absorbing member constituted by a spring wire bridge;

Fig. 4 is a section on the line IV-IV in Fig. 3;

Fig. 5 is a perspective view to an enlarged scale of one-half of a linkage included in Fig. 3; and

Fig. 6 is an exploded view in perspective of the rotary actuator and the linkage.

The mechanism comprises two toggle linkages 67, 68 and 70, H. The link 6'! of the primary toggle carries a roller-stop 66 which is forced outwardly from between two opposedand slightly inclined faces '62! and 63! by pressure exerted by these faces when a load is supported by the jaws 62, 63. The greater proportion of this thrust is taken by an anchorage 69, but since the toggle is not quite in alignment a small portion of the thrust is taken by the secondary toggle, the link of which is connected to the central pivot of the primary toggle.

The secondary toggle is made self-aligning by the provision of abutting inclined surfaces 2| and 22 on the links 10 and II respectively, as seen most clearly in Figs. 5 and 6. The toggle is thus allowed to collapse in only one direction, as seen in Fig. 2. The link H is further pivoted to the spindle 12 of a rotary armature 13, being forked to provide two arms H I and H2, one lying on each side of the armature. The armature is slotted at 23 on each side for the reception of the two arms HI and H2 the slots being of suffiicent width to allow a certain degree of relative angular displacement between the armature and the link H.

The armature is enclosed in a cylindrical cavity 14, the walls of which are provided with four soft the link H, causing the toggle to collapse into the position shown in Fig. 2. This movement of the armature separates the contacts Ti and -i8and interrupts the excitation of the armature.

In order to prevent the collapse otthe-togglebefore the armature is excited, the armature is impelled in a clockwise direction as seen in the drawings by a spiral clock spring 2%. Thisurges the side 2'. of the slot 23 towards theupperside" of the link H, the pressure being transmittedby' way of a shock-absorbing member, which latter takestheform of a resilient pad 23 inthe mechanisnr shown in Figs: Land 2 and oi a spring wire bridge 29in the mechanism shown in Fig. 3. In either case the member serves to absorb any shock whichmay be transmitted-from the link 'H-- to the armature 13. In extreme cases the shock might, without-the provision of theshockabsorbing member, be sufficient to cause the armature to rotate into the position shown in Fig.- 2, thereby causing the toggle TEL-H to collapse.

The spring wire bridge 29 shown in Fig; 3 and seen more clearly in Fig. 6 comprises two arms 3% attached to one of the poles 2% and joined by. a circular cross-member 3|. Under: the influence ofthespiral spring 26 thecross-member Si is pressed-into contact with the knuckleof the toggle, where it rests ina groove 32: of vsection cut across-bothlinks In and H ofthe toggle. The groove provides a positive look so. that any incipient movement-of the toggle is directly opposed by the. shear: resistance of the bridge 3!, and 7 its formation: in V-section in conjunction with the circular section of the cross-member prevents any back-lash between the sides of the groove and the cross-member. When the armature is energised its rotation operates first to relieve the strain in the bridge and then to remove the latter from the groove 32, preparatory to the impingement of the side 25-of-the slott23- against the underside of the link H to collapseftlie toggle.

What I claim as my invention and desire to secure by Letters Patent is:

l. A tripping mechanism for a releasable attachment of the type described, comprising a toggle linkage a rotary actuator mounted adjacent the said linkage and adapted upon rotation to initiate collapse of said linkage, a holding member on said actuator adapted normally to restrain said toggle linkage in braced position, means for rotating said actuator, and a bridgeshaped spring having two arms attached to a holding member and a cross member arranged to press downwardly upon the linkage in aldirection to oppose collapse thereof, said'cross' member resting in a groove cut across the linkage.

29 A mechanism according to claim .l,.tlie cross member being, of circular cross section and the groove b'eingjV-shaped.

REGINALD ARTHUR FIRNIANJ REFERENCES. CITED The'following referencesare of record in=the file of this patent:

UNITED STATES PATENTS Number Name Date 1,866,293 Chandler Ju1y"5'; 1932 1;893;217 Babitch" Jan. 3; 1933 2,253,057 Moore" June 4; 1940 2,496,168 Lee'et a1 Jan. 31 1950 FOREIGN PATENTS- Num'ber Country Date 572,809 GreatB'ritaili Oct; 24; 19%5 

